Abrasive product and method of making and using the same

ABSTRACT

The present invention relates to an abrasive article having a shaped abrasive coating on a shaped backing and to a method of making and using the flexible abrasive article. The flexible abrasive article includes a backing bearing separated, shaped non-abrasive structures having a distal end spaced from the backing which are coated with a shaped abrasive coating. The method comprises providing the backing, applying to one surface of the backing a plurality of separated, shaped non-abrasive structures with distal ends, coating the distal ends with a curable composition containing abrasive particles, imparting a shaped configuration to the uncured coating and curing the coating.

RELATED APPLICATION

[0001] This application is a continuation-in-part of U.S. patentapplication Ser. No. 10/033,391, filed Dec. 28, 2001, which is acontinuation-in-part of U.S. patent application Ser. No. 09/850,661,filed May 7, 2001, which is a continuation-in-part of U.S. patentapplication Ser. No. 09/706,033, filed Nov. 3, 2000; and U.S. patentapplication Ser. No. 10/137,134, filed Apr. 30, 2002, which is acontinuation-in-part of U.S. patent application Ser. No. 09/850,661,filed May 7, 2001, which is a continuation-in-part of U.S. patentapplication Ser. No. 09/706,033, filed Nov. 3, 2000. Each of these priorapplications is incorporated herein by reference.

FIELD OF THE INVENTION

[0002] The present invention relates generally to abrasive articleshaving a shaped abrasive coating on a non-abrasive shaped backing and toa method of making and using the abrasive article.

BACKGROUND OF THE INVENTION

[0003] In the abrasive industry there is a trend to finer and finersurface finish. Naturally, to achieve these finer surface finishes,smaller sized abrasive particles are employed in the abrasive article.In some instances the particle size of these small sized abrasiveparticles is less than 50 μm, typically less than 25 μm and sometimesless than 10 μm. In some instances loose abrasive slurries are employedrather than using fixed abrasive articles where the abrasive particlesmay be bonded together (to provide a bonded abrasive product) or to abacking (to provide a coated abrasive product). Many years ago, theseloose abrasive slurries were capable of achieving surface finishes thatwere not previously obtainable with fixed abrasives. Over the lastyears, however, advances in fixed abrasives, especially coatedabrasives, have enabled coated abrasives to effectively replace looseabrasive slurries in certain applications and thereby avoid the liquidhandling equipment required for, and the waste disposal problemsassociated with, the use of slurries.

[0004] In many instances to achieve a fine surface finish, the polishingprocess is done in the presence of a fluid, typically water or someother type of lubricant. The fluid serves several purposes includingminimizing heat build up and serving as a medium to remove the swarf ordebris generated during polishing. If the swarf is not effectivelyremoved during polishing, it is possible for the swarf to becomere-deposited on the abrasive coating and thereby may cause coarse andundesirable scratches. Thus, it is imperative that the swarf be removedto provide efficient fluid flow at the interface between the abrasivecoating and the workpiece surface being polished.

[0005] For all of the benefits of the fluid, there are sometimesdrawbacks. For instance, with the very small abrasive particles, theresulting outer surface of the abrasive coating may be relativelysmooth. The combination of the fluid and smooth abrasive coating hasbeen known to create what is known in the industry as “stiction,”whereby the fluid will act like adhesive between the abrasive coatingand the workpiece surface to cause these surfaces to stick together withunwanted results.

[0006] Stiction typically occurs in lapping type coated abrasiveproducts. There are two common types of coated abrasive products. Thefirst type has the abrasive particles bonded to the backing by means ofa make coat. Overlying the abrasive grains is a size coat, which furtherreinforces the abrasive grains. In this first type, there is essentiallyone or two layers of abrasive particles. In the fine grades, theabrasive particles are so small that the resulting coated abrasive mayexhibit a relatively short life. The second coated abrasive constructionhas the abrasive particles dispersed, typically uniformly dispersed, inthe binder. This second construction is sometimes referred to as a“lapping film.” The lapping film may have longer life because theretypically are multiple layers of abrasive particles as compared to theconstruction with the make and size coats. Likewise, the lapping filmmay produce a finer surface finish because the abrasive particles aremore embedded in a binder. Conversely, lapping films tend to have lowercut rates since the first type construction tends to have more abrasiveparticles protruding.

[0007] Stiction tends to occur more frequently with lapping-typeconstruction because the abrasive particles are embedded in the binderto provide a smooth surface. Various lapping type products have beenprovided with an abrasive coating which is shaped or structured, i.e.,having raised portions and recessed portions. These products are sold by3M Company under the trade designation “TRIZACT™” abrasive products.They are generally described in U.S. Pat. No. 5,152,917 (Pieper, etal.). Other lapping products are also described in U.S. Pat. No.5,489,235 (Gagliardi, et al.).

Other Related Art

[0008] U.S. Pat. No. 2,115,897 (Wooddell et al.) teaches an abrasivearticle having a backing having attached thereto by an adhesive aplurality of bonded abrasive segments. These bonded abrasive segmentscan be adhesively secured to the backing in a specified pattern.

[0009] U.S. Pat. No. 2,242,877 (Albertson) teaches a method of making acompressed abrasive disc. Several layers of coated abrasive fibre discsare placed in a mold and then subjected to heat and pressure to form thecompressed center disc. The mold has a specified pattern, which thentransfers to the compressed center disc, thus rendering a pattern coatedabrasive article.

[0010] U.S. Pat. No. 2,755,607 (Haywood) teaches a coated abrasive inwhich there are lands and grooves of abrasive portions. An adhesive coatis applied to the front surface of a backing and this adhesive coat isthen combed to create peaks and valleys. Next abrasive grains areprojected into the adhesive followed by solidification of the adhesivecoat.

[0011] U.S. Pat. No. 3,048,482 (Hurst) discloses an abrasive articlecomprising a backing, a bond system and abrasive granules that aresecured to the backing by the bond system. The abrasive granules are acomposite of abrasive grains and a binder which is separate from thebond system. The abrasive granules are three dimensional and arepreferably pyramidal in shape. To make this abrasive article, theabrasive granules are first made via a molding process. Next, a backingis placed in a mold, followed by the bond system and the abrasivegranules. The mold has patterned cavities therein which result in theabrasive granules having a specified pattern on the backing.

[0012] U.S. Pat. No. 3,605,349 (Anthon) pertains to a lapping typeabrasive article. Binder and abrasive grain are mixed together and thensprayed onto the backing through a grid. The presence of the gridresults in a patterned abrasive coating.

[0013] U.S. Pat. No. 3,498,010 (Hagihara) describes a flexible grindingdisc comprising an abrasive filled cured resin composite. The discfurther comprises a structured surface formed by a molding process.

[0014] Great Britain Patent Application No. 2,094,824 (Moore) pertainsto a patterned lapping film. The abrasive/binder resin slurry isprepared and the slurry is applied through a mask to form discreteislands. Next, the binder resin is cured. The mask may be a silk screen,stencil, wire or a mesh.

[0015] U.S. Pat. Nos. 4,644,703 (Kaczmarek et al.) and 4,773,920(Chasman et al.) concern a lapping abrasive article comprising a backingand an abrasive coating adhered to the backing. The abrasive coatingcomprises a suspension of lapping size abrasive grains and a bindercured by free radical polymerization. The abrasive coating can be shapedinto a pattern by a rotogravure roll.

[0016] Japanese Patent Application No. JP 62-238724A (Shigeharu,published Oct. 19, 1987) describes a method of forming a large number ofintermittent protrusions on a substrate. Beads of pre-cured resin areextrusion molded simultaneously on both sides of the plate andsubsequently cured.

[0017] U.S. Pat. No. 4,930,266 (Calhoun et al.) teaches a patternedabrasive sheeting in which the abrasive granules are strongly bonded andlie substantially in a plane at a predetermined lateral spacing. In thisinvention the abrasive granules are applied via an impingement techniqueso that each granule is essentially individually applied to the abrasivebacking. This results in an abrasive sheeting having a preciselycontrolled spacing of the abrasive granules.

[0018] U.S. Pat. No. 5,014,468 (Ravipati et al.) pertains to a lappingfilm intended for ophthalmic applications. The lapping film comprises apatterned surface coating of abrasive grains dispersed in a radiationcured adhesive binder. To make the patterned surface an abrasive/curablebinder slurry is shaped on the surface of a rotogravure roll, the shapedslurry removed from the roll surface and then subjected to radiationenergy for curing.

[0019] U.S. Pat. No. 5,015,266 (Yamamoto) pertains to an abrasive sheetmade by uniformly coating an abrasive/adhesive slurry over an embossedsheet to provide an abrasive coating which on curing has high and lowabrasive portions formed by the surface tension of the slurry,corresponding to the irregularities of the base sheet.

[0020] U.S. Pat. No. 5,107,626 (Mucci) teaches a method of providing apatterned surface on a substrate by abrading with a coated abrasivecontaining a plurality of precisely shaped abrasive composites. Theabrasive composites are in a non-random array and each compositecomprises a plurality of abrasive grains dispersed in a binder.

[0021] Japanese Patent Application No. 02-083172 (Tsukada et al.,published Mar. 23, 1990) teaches a method of a making a lapping filmhaving a specified pattern. An abrasive/binder slurry is coated intoindentations in a tool. A backing is then applied over the tool and thebinder in the abrasive slurry is cured. Next, the resulting coatedabrasive is removed from the tool. The binder can be cured by radiationenergy or thermal energy.

[0022] Japanese Patent Application No. JP 4-159084 (Nishio et al.,published Jun. 2, 1992) teaches a method of making a lapping tape. Anabrasive slurry comprising abrasive grains and an electron beam curableresin is applied to the surface of an intaglio roll or indentationplate. Then, the abrasive slurry is exposed to an electron beam whichcures the binder and the resulting lapping tape is removed from theroll.

[0023] U.S. Pat. No. 5,190,568 (Tselesin) describes a coated abrasivehaving a plurality of peaks and valleys. Abrasive particles are embeddedin and on the surface of the composite structure.

[0024] U.S. Pat. No. 5,199,227 (Ohishi) describes a surface treatingtape comprising a plurality of particulate filled resin protuberances ona substrate. The protuberances are closely spaced Bernard cells coatedwith a layer of premium abrasive particles.

[0025] U.S. Pat. No. 5,219,462 (Bruxvoort et al.), assigned to the sameassignee as the present application, teaches a method for making anabrasive article. An abrasive/binder/expanding agent slurry is coatedsubstantially only into the recesses of an embossed backing. Aftercoating, the binder is cured and the expanding agent is activated. Thiscauses the slurry to expand above the surface of the embossed backing.

[0026] U.S. Pat. No. 5,435,816 (Spurgeon et al.), assigned to the sameassignee as the present application, teaches a method of making anabrasive article. In one aspect of this patent application, anabrasive/binder slurry is coated into recesses of an embossed substrate.Radiation energy is transmitted through the embossed substrate and intothe abrasive slurry to cure the binder.

[0027] U.S. Pat. No. 5,437,754 (Calhoun), assigned to the same assigneeas the present application, teaches a method of making an abrasivearticle. An abrasive slurry is coated into recesses of an embossedsubstrate. The resulting construction is laminated to a backing and thebinder in the abrasive slurry is cured. The embossed substrate isremoved and the abrasive slurry adheres to the backing.

[0028] U.S. Pat. No. 5,672,097 (Hoopman), assigned to the same assigneeas the present application, teaches an abrasive article where thefeatures are precisely shaped but vary among themselves.

[0029] European Patent No. 702,615 (Romero, published Oct. 22, 1997)describes an abrasive article having a patterned abrasive surface. Theabrasive article has a plurality of raised and recessed portionscomprising a thermoplastic material, the raised portions furthercomprising a layer of adhesive and abrasive material while the recessedportions are devoid of abrasive material.

[0030] U.S. Pat. No. 5,785,784 (Chesley et al.) pertains to an abrasivearticle having a first and a second, opposite, major surface. Amechanical fastener is formed on one surface and precisely shapedabrasive composites are applied via a production tool on the oppositemajor surface.

[0031] U.S. Pat. No. 6,299,508 (Gagliardi et al.) describes an abrasivearticle having a plurality of grinding-aid containing protrusionsintegrally molded to the surface of a backing. The protrusions arecontoured so as to define a plurality of peaks and valleys, whereinabrasive particles cover at least a portion of the peaks and valleys.

[0032] What is desired in the industry is an abrasive article thatminimizes any swarf or debris build up at the abrading interface;quickly generates fine surface finish; has long life; and minimizesstiction.

SUMMARY OF THE INVENTION

[0033] The invention provides an abrasive product, a method of makingthe same and a method of using the same. The novel abrasive product hasa shaped abrasive coating on a shaped backing that provides a surfacewhich has depressed areas which permit accumulated debris to collectwithout disturbing the raised abrasive portions of the abrasive product.Compared to a planar backing, the shaped backing transfers highergrinding pressure to the workpiece, thereby increasing the rate offinish refinement.

[0034] In one aspect, the invention provides an abrasive articlecomprising:

[0035] a. a backing having a first major surface and an opposite secondmajor surface;

[0036] b. a plurality of separated, shaped non-abrasive structures, eachstructure having an attachment end attached to said first major surfaceand a distal end spaced from said first major surface with said shapedstructures comprising distal ends being aligned generally in the sameplane;

[0037] c. a shaped abrasive coating comprised of abrasive particles in abond system having raised areas and depressed areas coated over at leastsaid distal ends.

[0038] The invention further provides a method of making an abrasivearticle. The method comprises:

[0039] a. providing a backing having a first major surface and anopposite second major surface;

[0040] b. applying a plurality of separated, shaped non-abrasivestructures to said first major surface, each of said structures havingan attachment end attached to said first major surface and a distal endspaced from said first major surface with shaped structures comprisingdistal ends aligned generally in the same plane;

[0041] c. coating at least said distal ends with a coating compositioncomprising abrasive particles in a curable composition which will cureto provide a bond system for the abrasive particles;

[0042] d. imparting a shaped configuration to the coating composition toprovide on curing a shaped abrasive coating having raised areas anddepressed areas; and

[0043] e. curing the curable composition.

[0044] The invention further provides a method of finishing a surface ofa substrate, the method comprising:

[0045] a. contacting a surface of a workpiece with an abrasive articlecomprising:

[0046] (1) a backing having a first major surface and an opposite secondmajor surface;

[0047] (2) a plurality of separated, shaped non-abrasive structures,each structure having an attachment end attached to said first majorsurface and a distal end spaced from said first major surface with saidshaped structures comprising distal ends being aligned generally in thesame plane; and

[0048] (3) a shaped abrasive coating comprised of abrasive particles ina bond system having raised areas and depressed areas coated over atleast said distal ends; and

[0049] b. relatively moving the abrasive article and/or said workpieceto modify the surface of the workpiece.

[0050] Typically, in use a liquid such as water is applied to theworking surface of the coated abrasive product to facilitate removal ofswarf and grinding debris.

[0051] The abrasive product of the present invention is characterized byhaving a backing which preferably includes on one surface thereof aplurality of separated, shaped structures. Each structure has anattachment end attached to the surface of the backing and a distal endspaced from the surface of the backing with the distal ends beinggenerally aligned in the same plane. A shaped or structured abrasivecoating comprised of abrasive particles in a bond system is coated overat least the distal ends of the shaped structures.

Definition of Terms

[0052] The term “backing” shall mean a shaped, preferably flexiblebacking onto which shaped features and shaped abrasive composites are tobe subsequently added.

[0053] The term “shaped non-abrasive structures” shall mean structurescomposed of materials which do not include abrasive particles.

[0054] The term “shaped abrasive coating” shall mean a coating of acured binder and abrasive material that has an exposed or workingsurface which includes raised portions and recessed portions.

[0055] The term “at least partially cured” means “part” or “all” of thecurable binder precursor material has been cured to such a degree thatit is handleable and collectable. The term “at least partially cured”does not mean that part or all of the curable binder precursor is alwaysfully cured, but that it is sufficiently cured, after being at leastpartially cured, to be handleable and collectable.

[0056] As used herein, the expression “handleable and collectable”refers to material that will not substantially flow or experience asubstantial change in shape if subjected to an applied force that tendsto strain or deform a body.

[0057] The phrase “fully cured” shall mean the binder precursor issufficiently cured so that the resulting product will function as anabrasive article, e.g. a coated abrasive article.

[0058] The term “separated, shaped structures” shall mean bodies whichindividually have a height and a volume contained within an area definedeither by its distal or attachment end in any regular or irregularconfiguration which may include a cylindrical shape having a rounddistal end or attachment end, a box-shape which may include a square orrectangular distal or attachment end, a truncated three-side orfour-sided pyramidal shape, or an irregular shape.

[0059] The term “separated” when referring to “shaped structures” shallmean that adjacent structures in the same abrasive product will have agap therebetween and includes adjacent structures separated by a gapwhich may touch and be a part of one another either at touching cornersof a box-shaped structure or touching sides of a cylindrical shapedstructure.

[0060] The phrase “said distal ends being aligned generally in the sameplane” shall mean that a substantial portion of the distal ends of theshaped structures lie mainly in the same plane although the surface mayinclude additional shaped structures which have distal ends which fallshort of lying in such a plane.

[0061] The term “applying a plurality of separated, shaped structures tothe first surface” shall include physically attaching bodies to onesurface of the backing of a composition which is not the same as that ofthe backing or by molding a backing in a mold which creates thestructures and the backing at the same time with the appropriate shapesfor the structures. The term “applying” also includes embossing abacking to provide an undulated surface which includes embossed raisedportions wherein the height of the shaped structure would be defined bya wall derived from the backing being imparted with an embossedconfiguration and a distal end which, likewise, originates from theembossed backing.

[0062] The term “bearing area” shall mean the cumulative area of theabrasive coating on the distal ends in the same plane.

[0063] The term “percent bearing area” shall mean the total bearing areaas defined above as compared to the total backing area on which theseparated, shaped structures are applied X 100.

[0064] The abrasive product of the present invention has a long usefullife because of the existence of spaces between the shaped bodies whichprovides a collection area for swarf and debris generated duringfinishing. Thus, the abrasive product can use very fine abrasive grainsto provide extremely fine surface finishes to any of a variety ofworkpiece surfaces. The product of the invention provides a viablereplacement for utilizing loose abrasive slurries and obviates the needfor liquid handling equipment normally associated with slurries and theneed for finding appropriate disposal sites for used slurries. Thepresence of the recessed areas between the shaped bodies that are coatedwith shaped abrasive coatings provides for efficient fluid flow at theworking face of the abrasive product of the invention withoutundesirable “stiction” which is normally encountered in smooth-surfacedlapping films on smooth-surfaced workpiece surfaces. Compared to aplanar backing, the shaped backing transfers higher grinding pressure tothe workpiece, thereby increasing the rate of finish refinement. Theproducts of the invention, having a shaped-surface, provide forcontrolled breakdown of the abrasive layer which provides for a constantcut rate and extended use life of the abrasive coating. The products ofthe invention also provide for reduced heat generation in use becausethe abrasive surface is not continuous. They further provide betterconformance to short range (e.g., orange peel) and long range (e.g.,auto body contours) surface textures.

BRIEF DESCRIPTION OF THE DRAWINGS

[0065]FIG. 1 is an enlarged schematic cross-sectional drawnrepresentation of a portion of an abrasive product according to thepresent invention.

[0066]FIG. 2 is a schematic representation of one process for making anabrasive article according to the present invention.

[0067]FIG. 3 is a photomicrograph taken at a magnification of 10 X ofthe top surface of a coated abrasive product made in accordance with thepresent invention.

[0068]FIG. 4 is a photomicrograph taken at a magnification of 10 X ofthe top surface of a coated abrasive product made in accordance with thepresent invention.

[0069]FIG. 5 is a top plane view of a roller for making a productiontool useful for making the shaped abrasive layer of articles accordingto the present invention.

[0070]FIG. 6 is an enlarged sectional view of one segment of the rolldepicted in FIG. 5 taken at line 6-6 to show surface detail.

[0071]FIG. 7 is an enlarged sectional view of another segment of thepatterned surface of the roll depicted in FIG. 5, taken at line 7-7.

[0072]FIGS. 8 and 9 are an enlarged drawn plane view representations ofa pattern used to make tooling for Examples 1-16

DETAILED DESCRIPTION OF THE INVENTION

[0073]FIG. 1 shows an enlarged schematic cross-sectional drawnrepresentation of a portion of an abrasive product 10 according to thepresent invention. Abrasive product 10 includes backing 11 having afirst major surface 14 and an opposite major surface 15. A plurality ofseparated, shaped structures 12 are attached to first major surface 14.Alternatively, the shaped structures may be unitarily formed from thebacking, as herein described. Each shaped structure 12 includes anattachment end 16 which is attached to first major surface 14 and adistal end 17 which is spaced from first major surface 14 by the height20 of the shaped structure. A shaped abrasive layer 13 is coated over atleast distal ends 17 of separated shaped structures 12. Shaped abrasivelayer 13 is characterized by including abrasive particles 21 in asuitable bond system 22 and includes raised portions 18 and depressedportions 19.

[0074] As shown in the photomicrograph of FIG. 3, viewed from above,shaped structures 12 may have a circular configuration, or a squareconfiguration as depicted in the photomicrograph of FIG. 4.Alternatively, when viewed from above, the shaped structure may have ahexagonal configuration or the configuration of an annulus. The shapedstructures need not all have the same structure or the same shape. Forexample, a product having circular shapes varying in diameter from 10 mmto 100 mm may be provided with smaller diameter shapes being locatedbetween larger diameter shapes.

[0075] The shaped structures may be randomly positioned on backing 11 orthey may be aligned in rows in at least one direction, but preferablythey are aligned in rows in at least two directions. When aligned inrows, a channel is provided by the space between rows. The channel ispreferably free of any abrasive coating, although it may be coated withabrasive, if desired.

[0076] Preferred materials for forming shaped structures 12 includepolymeric materials which may be solid or may comprise a foam.

[0077] Distal ends 17 of shaped structures 12 are preferably flat,although they may include other configurations which may be embossedwith a pattern, curved, domed or otherwise configured.

[0078] The spacing from the backing surface of the distal ends of theshaped structures may be any convenient spacing, but preferably is atleast about 0.05 mm and typically about 0.25 to about 20 mm.

[0079] Backing 11 may be any conventional backing material describedhereinafter useful as a coated abrasive backing. Preferred backingmaterials include polymeric films and foamed sheet materials.

[0080] Backing 11 may be coated with an abrasive composition accordingto the methods described in U.S. Pat. No. 5,435,816 (Spurgeon et al.)and U.S. Pat. No. 5,667,541 (Klun et al.), incorporated herein byreference.

[0081] The backing 11 may further comprise a laminate having one part ofa two part attachment system onto which is laminated (on the smooth sideof the attachment system layer) a second layer. The lamination ofbacking 11 may serve as a means of improving dimensional stabilityduring coating and subsequent use, as described in U.S. patentapplication Ser. No. 09/850,661 (Schutz et al.) filed May 7, 2001, whichis incorporated herein by reference.

[0082] Each abrasive composite layer includes components important tosurface modification characteristics and the durability of an abrasivearticle. The components of the abrasive composite layers and otherembodiments of the invention are discussed in the following sections ofthe patent application.

[0083] Shaped Backing

[0084] There are numerous means to make the backing with the shapedstructures. In one aspect, the shaped structures may be laminated oradhered to the first major surface of the backing. Any suitablelamination technique or adhesive may be employed. In another aspect, theshaped structures are formed on the first major surface of the backing.There are numerous methods to achieve this.

[0085] In the first method, the shaped structure is formed by acontinuous molding process. In this process, it is generally preferredthat the shaped structures be made from an acrylate and/or epoxy resinthat is capable of being crosslinked into an acrylate and/or epoxypolymer. Additional details on acrylate resins and epoxy resin may befound in the binder section of this patent application. FIG. 2illustrates an apparatus 23 for applying a shaped coating to the firstmajor surface of the backing. A production tool 24 is in the form of abelt having a cavity-bearing contacting a surface 30, an oppositebacking surface 38 and appropriately sized cavities within contactingsurface 30. Backing 25 having a first major surface 26 and a secondmajor surface 27 is unwound from roll 28. At the same time backing 25 isunwound from roll 28, the production tool 24 is unwound from roll 29.The contacting surface 30 of production tool 24 is coated with a mixtureof precursor material that will form the shaped structure at coatingstation 31. The mixture can be heated to lower the viscosity thereofprior to the coating step. The coating station 31 can comprise anyconventional coating means, such as knife coater, drop die coater,curtain coater, vacuum die coater, roll coater or an extrusion diecoater. After the contacting surface 30 of production tool 24 is coated,the backing 25 and the production tool 24 are brought together such thatthe mixture wets the first major surface 26 of the backing 25. In FIG.2, the mixture is forced into contact with the backing 25 by means of acontact nip roll 33, which also forces the productiontool/mixture/backing construction against a support drum 35. Next, asufficient dose of radiation energy is transmitted by a source ofradiation energy 37 through the back surface 38 of production tool 24and into the mixture to at least partially cure the binder precursor,thereby forming a shaped, handleable structure 39. The production tool24 is then separated from the shaped, handleable structure 39.Separation of the production tool 24 from the shaped handleablestructure 39 occurs at roller 40. The angle α between the shaped,handleable structure 39 and the production tool 24 immediately afterpassing over roller 40 is preferably steep, e.g., in excess of 30°, inorder to bring about clean separation of the shaped, handleablestructure 39 from the production tool 24. The production tool 24 isrewound as roll 41 so that it can be reused. Shaped, handleablestructure 39 is wound as roll 43. If the binder precursor has not beenfully cured, it can then be fully cured by exposure to an additionalenergy source, such as a source of thermal energy or an additionalsource of radiation energy, to form the backing with the shapedstructures. Alternatively, full cure may eventually result without theuse of an additional energy source to form the coated abrasive article.As used herein, the phrase “full cure” and the like means that thebinder precursor is sufficiently cured so that the resulting productwill function as a backing for a coated abrasive article.

[0086] Typically the production tool is used to provide a polymericcomposite layer with an array of either precisely or irregularly shapedstructures. The production tool has a surface containing a plurality ofcavities. These cavities are essentially the inverse shape of thepolymeric structures and are responsible for generating the shape andplacement of the polymeric structures. These cavities may have anygeometric shape that is the inverse shape to the geometric shapessuitable for the shaped structures onto which the abrasive layer iscoated. Preferably, the shape of the cavities is selected such that thesurface area of the shaped structure decreases away from the backing.The production tool can be a belt, a sheet, a continuous sheet or web, acoating roll such as a rotogravure roll, a sleeve mounted on a coatingroll, or die. Additional details on production tools may be found in thesection for “Making Abrasive Coating.”

[0087] In another method of making a shaped backing, the curable resincan be coated onto the surface of a rotogravure roll. The backing comesinto contact with the rotogravure roll and the curable resin wets thebacking. The rotogravure roll then imparts a pattern or texture into thecurable resin. Next, the resin/backing combination is removed from therotogravure roll and the resulting construction is exposed to conditionsto cure the precursor polymer subunits such that shaped polymer featuresare formed. A variation of this process is to coat the curable resinonto the backing and bring the backing into contact with the rotogravureroll.

[0088] The rotogravure roll may impart desired patterns such as ahexagonal array, truncated ridges, lattices, spheres, truncatedpyramids, cubes, blocks, or rods. The rotogravure roll may also impart apattern such that there is a land area between adjacent polymericfeatures. Alternatively, the rotogravure roll can impart a pattern suchthat the backing is exposed between adjacent polymeric shapes.Similarly, the rotogravure roll can impart a pattern such that there isa mixture of polymeric shapes.

[0089] In still another method is to spray or coat the curable resinlayer through a screen to generate a pattern in the curable resin layer.Then the precursor polymer subunits are cured to form the polymericstructures. The screen can impart any desired pattern such as ahexagonal array, truncated ridges, lattices, spheres, pyramids,truncated pyramids, cubes, blocks, or rods. The screen may also impart apattern such that there is a land area between adjacent polymericstructures. Alternatively, the screen may impart a pattern such that thebacking is exposed between adjacent polymeric structures. Similarly, thescreen may impart a pattern such that there is a mixture of polymericshapes.

[0090] Another method of making a shaped backing is to laminate atextured, shaped or embossed layer onto the first major surface of thebacking. The resulting shaped laminate can then be used as the backingonto which a shaped abrasive layer is coated onto the textured, shapedor embossed layer. This textured, shaped or embossed layer can include,for example, scrims or screens.

[0091] Yet another alternative method for making a shaped backing is topattern-coat a curable resin onto a generally planar backing, whereinthe resin contains a component that can subsequently be expanded suchthat the dimensions of the pattern-coated resin features increase afterexpansion. This expansion preferably takes place before curing of theresin, but can also take place after curing. Examples of components thatcan be expanded upon changes in process conditions include expandablemicrospheres, such as available under the MICROPEARL tradename fromPierce-Stevens Corp, Buffalo, N.Y. A modification to this method is thatthe polymer microspheres are expanded prior to adding to the curableresin. The curable resin is pattern-coated into structures that are ofsufficient height, and subsequently cured, yielding a shaped backingwith features comprised of polymeric foam.

[0092] A backing consisting of shaped structures can also be formed bythe continuous coating of a layer of curable resin wherein the resincontains a component that can subsequently be expanded in a pattern bylocal irradiation with specific wavelength range of electromagneticradiation, e.g. infrared. Preferably, the curable resin layer is curedsubsequent to the patterned expansion of the expandable component.

[0093] In yet another method, the backing is embossed to create theshaped structures. For example, thermoplastic films or foams such asnylon, propylene, polyester, polyethylene and the like, may be thermallyembossed. The embossing tool has essentially the inverse of the desiredshape and dimensions of the shaped structures.

[0094] The particular type and construction of the backing and/or shapedstructures will depend upon many factors and mainly upon the desiredproperties of the final abrasive article for the intended polishingapplication. For example where a flexible abrasive article is desired, afoam backing and foam structures may be desirable. Alternatively wherehigh cut rates are desired, a stiffer backing may be preferred. Oneskilled in the art will be able to formulate a backing and shapedstructures that exhibit the appropriate properties.

[0095] Abrasive Particles

[0096] An abrasive article of the present invention typically comprisesat least one abrasive composite layer that includes a plurality ofabrasive particles dispersed in precursor polymer subunits. The binderis formed from a binder precursor comprising precursor polymer subunits.The abrasive particles may be uniformly dispersed in a binder oralternatively the abrasive particles may be non-uniformly dispersedtherein. It is preferred that the abrasive particles are uniformlydispersed in the binder so that the resulting abrasive article has amore consistent cutting ability.

[0097] The average particle size of the abrasive particles can rangefrom about 0.01 to 1500 micrometers, typically between 0.01 and 500micrometers, and most generally between 1 and 100 micrometers. The sizeof the abrasive particle is typically specified to be the longestdimension of the abrasive particle. In most cases there will be a rangedistribution of particle sizes. In some instances it is preferred thatthe particle size distribution be tightly controlled such that theresulting abrasive article provides a consistent surface finish on theworkpiece being abraded.

[0098] Examples of conventional hard abrasive particles include fusedaluminum oxide, heat treated aluminum oxide, white fused aluminum oxide,black silicon carbide, green silicon carbide, titanium diboride, boroncarbide, tungsten carbide, titanium carbide, diamond (both natural andsynthetic), silica, iron oxide, chromia, ceria, zirconia, titania,silicates, tin oxide, cubic boron nitride, garnet, fused aluminazirconia, sol gel abrasive particles and the like. Examples of sol gelabrasive particles can be found in U.S. Pat. Nos. 4,314,827 (Leitheiseret al.); 4,623,364 (Cottringer et al); 4,744,802 (Schwabel); 4,770,671(Monroe et al.) and 4,881,951 (Wood et al.), all incorporatedhereinafter by reference.

[0099] The term abrasive particle, as used herein, also encompassessingle abrasive particles bonded together with a polymer to form anabrasive agglomerate. Abrasive agglomerates are further described inU.S. Pat. Nos. 4,311,489 (Kressner); 4,652,275 (Bloecher et al.);4,799,939 (Bloecher et al.), and 5,500,273 (Holmes et al.).Alternatively, the abrasive particles may be bonded together by interparticle attractive forces.

[0100] The abrasive particle may also have a shape associated with it.Examples of such shapes include rods, triangles, pyramids, cones, solidspheres, hollow spheres and the like. Alternatively, the abrasiveparticle may be randomly shaped.

[0101] Abrasive particles can be coated with materials to provide theparticles with desired characteristics. For example, materials appliedto the surface of an abrasive particle have been shown to improve theadhesion between the abrasive particle and the polymer. Additionally, amaterial applied to the surface of an abrasive particle may improve thedispersibility of the abrasive particles in the precursor polymersubunits. Alternatively, surface coatings can alter and improve thecutting characteristics of the resulting abrasive particle. Such surfacecoatings are described, for example, in U.S. Pat. Nos. 5,011,508 (Waldet al.); 3,041,156 (Rowse et al.); 5,009,675 (Kunz et al.); 4,997,461(Markhoff-Matheny et al.); 5,213,591 (Celikkaya et al.); 5,085,671(Martin et al.) and 5,042,991 (Kunz et al.), the disclosures of whichare incorporated herein by reference.

[0102] Fillers

[0103] An abrasive article of this invention may comprise an abrasivecoating which further comprises a filler. A filler is a particulatematerial with an average particle size range between 0.1 to 50micrometers, typically between 1 to 30 micrometers. Examples of usefulfillers for this invention include metal carbonates (such as calciumcarbonate, calcium magnesium carbonate, sodium carbonate, magnesiumcarbonate), silica (such as quartz, glass beads, glass bubbles and glassfibers), silicates (such as talc, clays, montmorillonite, feldspar,mica, calcium silicate, calcium metasilicate, sodium aluminosilicate,sodium silicate), metal sulfates (such as calcium sulfate, bariumsulfate, sodium sulfate, aluminum sodium sulfate, aluminum sulfate),gypsum, vermiculite, sugar, wood flour, aluminum trihydrate, carbonblack, metal oxides (such as calcium oxide, aluminum oxide, tin oxide,titanium dioxide), metal sulfites (such as calcium sulfite),thermoplastic particles (such as polycarbonate, polyetherimide,polyester, polyethylene, polysulfone, polystyrene,acrylonitrile-butadiene-styrene block copolymer, polypropylene, acetalpolymers, polyurethanes, nylon particles) and thermosetting particles(such as phenolic bubbles, phenolic beads, polyurethane foam particlesand the like). The filler may also be a salt such as a halide salt.Examples of halide salts include sodium chloride, potassium cryolite,sodium cryolite, ammonium cryolite, potassium tetrafluoroborate, sodiumtetrafluoroborate, silicon fluorides, potassium chloride, magnesiumchloride. Examples of metal fillers include, tin, lead, bismuth, cobalt,antimony, cadmium, iron titanium. Other miscellaneous fillers includesulfur, organic sulfur compounds, graphite and metallic sulfides andsuspending agents.

[0104] An example of a suspending agent is an amorphous silica particlehaving a surface area less than 150 meters square/gram that iscommercially available from DeGussa Corp., Rheinfelden, Germany, underthe tradename “OX-50.” The addition of the suspending agent can lowerthe overall viscosity of the abrasive slurry. The use of suspendingagents is further described in U.S. Pat. No. 5,368,619 (Culler)incorporated hereinafter by reference.

[0105] Abrasive Composite Binders

[0106] The abrasive coating of this invention is formed from a curableabrasive composite layer that comprise a mixture of abrasive particlesand precursor polymer subunits. The curable abrasive composite layerpreferably comprises organic precursor polymer subunits. The precursorpolymer subunits preferably are capable of flowing sufficiently so as tobe able to coat a surface. Solidification of the precursor polymersubunits may be achieved by curing (e.g., polymerization and/orcross-linking), by drying (e.g., driving off a liquid) and/or simply bycooling. The precursor polymer subunits may be an organic solvent borne,a water-borne, or a 100% solids (i.e., a substantially solvent-free)composition. Both thermoplastic and/or thermosetting polymers, ormaterials, as well as combinations thereof, maybe used as precursorpolymer subunits. Upon the curing of the precursor polymer subunits, thecurable abrasive composite is converted into the cured abrasivecomposite. The preferred precursor polymer subunits can be either acondensation curable resin or an addition polymerizable resin. Theaddition polymerizable resins can be ethylenically unsaturated monomersand/or oligomers. Examples of useable crosslinkable materials includephenolic resins, bismaleimide binders, vinyl ether resins, aminoplastresins having pendant alpha, beta unsaturated carbonyl groups, urethaneresins, epoxy resins, acrylate resins, acrylated isocyanurate resins,urea-formaldehyde resins, isocyanurate resins, acrylated urethaneresins, acrylated epoxy resins, or mixtures thereof.

[0107] An abrasive composite layer may comprise by weight between about1 part abrasive particles to 90 parts abrasive particles and 10 partsprecursor polymer subunits to 99 parts precursor polymer subunits.Preferably, an abrasive composite layer may comprise about 30 to 85parts abrasive particles and about 15 to 70 parts precursor polymersubunits. More preferably an abrasive composite layer may comprise about40 to 70 parts abrasive particles and about 30 to 60 parts precursorpolymer subunits.

[0108] The precursor polymer subunits are preferably a curable organicmaterial (i.e., a polymer subunit or material capable of polymerizingand/or crosslinking upon exposure to heat and/or other sources ofenergy, such as electron beam, ultraviolet light, visible light, etc.,or with time upon the addition of a chemical catalyst, moisture, orother agent which cause the polymer to cure or polymerize). Precursorpolymer subunits examples include amino polymers or aminoplast polymerssuch as alkylated urea-formaldehyde polymers, melamine-formaldehydepolymers, and alkylated benzoguanamine-formaldehyde polymer, acrylatepolymers including acrylates and methacrylates alkyl acrylates,acrylated epoxies, acrylated urethanes, acrylated polyesters, acrylatedpolyethers, vinyl ethers, acrylated oils, and acrylated silicones, alkydpolymers such as urethane alkyd polymers, polyester polymers, reactiveurethane polymers, phenolic polymers such as resole and novolacpolymers, phenolic/latex polymers, epoxy polymers such as bisphenolepoxy polymers, isocyanates, isocyanurates, polysiloxane polymersincluding alkylalkoxysilane polymers, or reactive vinyl polymers. Theresulting binder may be in the form of monomers, oligomers, polymers, orcombinations thereof.

[0109] The aminoplast precursor polymer subunits have at least onependant alpha, beta-unsaturated carbonyl group per molecule or oligomer.These polymer materials are further described in U.S. Pat. Nos.4,903,440 (Larson et al.) and 5,236,472 (Kirk et al.), both incorporatedherein by reference.

[0110] Preferred cured abrasive composites are generated from freeradical curable precursor polymer subunits. These precursor polymersubunits are capable of polymerizing rapidly upon an exposure to thermalenergy and/or radiation energy. One preferred subset of free radicalcurable precursor polymer subunits include ethylenically unsaturatedprecursor polymer subunits. Examples of such ethylenically unsaturatedprecursor polymer subunits include aminoplast monomers or oligomershaving pendant alpha, beta unsaturated carbonyl groups, ethylenicallyunsaturated monomers or oligomers, acrylated isocyanurate monomers,acrylated urethane oligomers, acrylated epoxy monomers or oligomers,ethylenically unsaturated monomers or diluents, acrylate dispersions,and mixtures thereof. The term acrylate includes both acrylates andmethacrylates.

[0111] Ethylenically unsaturated precursor polymer subunits include bothmonomeric and polymeric compounds that contain atoms of carbon, hydrogenand oxygen, and optionally, nitrogen and the halogens. Oxygen ornitrogen atoms or both are generally present in the form of ether,ester, urethane, amide, and urea groups. The ethylenically unsaturatedmonomers may be monofunctional, difunctional, trifunctional,tetrafunctional or even higher functionality, and include both acrylateand methacrylate-based monomers. Suitable ethylenically unsaturatedcompounds are preferably esters made from the reaction of compoundscontaining aliphatic monohydroxy groups or aliphatic polyhydroxy groupsand unsaturated carboxylic acids, such as acrylic acid, methacrylicacid, itaconic acid, crotonic acid, isocrotonic acid, or maleic acid.Representative examples of ethylenically unsaturated monomers includemethyl methacrylate, ethyl methacrylate, styrene, divinylbenzene,hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropylacrylate, hydroxy propyl methacrylate, hydroxybutyl acrylate,hydroxybutyl methacrylate, lauryl acrylate, octyl acrylate, caprolactoneacrylate, caprolactone methacrylate, tetrahydrofurfuryl methacrylate,cyclohexyl acrylate, stearyl acrylate, 2 -phenoxyethyl acrylate,isooctyl acrylate, isobomyl acrylate, isodecyl acrylate, polyethyleneglycol monoacrylate, polypropylene glycol monoacrylate, vinyl toluene,ethylene glycol diacrylate, polyethylene glycol diacrylate, ethyleneglycol dimethacrylate, hexanediol diacrylate, triethylene glycoldiacrylate, 2-(2-ethoxyethoxy) ethyl acrylate, propoxylated trimethylolpropane triacrylate, trimethylolpropane triacrylate, glyceroltriacrylate, pentaerthyitol triacrylate, pentaerythritoltrimethacrylate, pentaerythritol tetraacrylate and pentaerythritoltetramethacrylate. Other ethylenically unsaturated materials includemonoallyl, polyallyl, or polymethallyl esters and amides of carboxylicacids, such as diallyl phthalate, diallyl adipate, orN,N-diallyladipamide. Still other nitrogen containing ethylenicallyunsaturated monomers include tris(2-acryloxyethyl) isocyanurate,1,3,5-tri(2-methyacryloxyethyl)-s-triazine, acrylamide,methylacrylamide, N-methyl-acrylamide, N,N-dimethylacrylamide,N-vinylpyrrolidone, or N-vinyl-piperidone.

[0112] A preferred precursor polymer subunits contains a blend of two ormore acrylate monomers. For example, the precursor polymer subunits maybe a blend of trifunctional acrylate and a monofunctional acrylatemonomers. An example of one precursor polymer subunits is a blend ofpropoxylated trimethylol propane triacrylate and 2-(2-ethoxyethoxy)ethyl acrylate. The weight ratios of multifunctional acrylate andmonofunctional acrylate polymers may range from about 1 part to about 90parts multifunctional acrylate to about 10 parts to about 99 partsmonofunctional acrylate.

[0113] It is also feasible to formulate a precursor polymer subunitsfrom a mixture of an acrylate and an epoxy polymer, e.g., as describedin U.S. Pat. No. 4,751,138 (Tumey et al.), incorporated herein byreference.

[0114] Other precursor polymer subunits include isocyanurate derivativeshaving at least one pendant acrylate group and isocyanate derivativeshaving at least one pendant acrylate group are further described in U.S.Pat. No. 4,652,274 (Boettcher et al.), incorporated herein by reference.The preferred isocyanurate material is a triacrylate oftris(hydroxyethyl) isocyanurate.

[0115] Still other precursor polymer subunits include diacrylateurethane esters as well as polyacrylate or polymethacrylate urethaneesters of hydroxy terminated isocyanate extended polyesters orpolyethers. Examples of commercially available acrylated urethanesinclude those under the tradename “UVITHANE 782,” available from MortonChemical, Moss Point, Miss.; “CMD 6600,” “CMD 8400,” and “CMD 8805,”available from UCB Radcure Specialties, Smyrna, Ga.; “PHOTOMER” resins(e.g., PHOTOMER 6010) from Henkel Corp., Hoboken, N.J.; “EBECRYL 220”(hexafunctional aromatic urethane acrylate), “EBECRYL 284” (aliphaticurethane diacrylate of 1200 diluted with 1,6-hexanediol diacrylate),“EBECRYL 4827” (aromatic urethane diacrylate), “EBECRYL 4830” (aliphaticurethane diacrylate diluted with tetraethylene glycol diacrylate),“EBECRYL 6602” (trifunctional aromatic urethane acrylate diluted withtrimethylolpropane ethoxy triacrylate), “EBECRYL 840” (aliphaticurethane diacrylate), and “EBECRYL 8402” (aliphatic urethane diacrylate)from UCB Radcure Specialties; and “SARTOMER” resins (e.g., “SARTOMER”9635, 9645, 9655, 963-B80, 966-A80, CN980M50, etc.) from Sartomer Co.,Exton, Pa.

[0116] Yet other precursor polymer subunits include diacrylate epoxyesters as well as polyacrylate or poly methacrylate epoxy ester such asthe diacrylate esters of bisphenol A epoxy polymer. Examples ofcommercially available acrylated epoxies include those under thetradename “CMD 3500,” “CMD 3600,” and “CMD 3700,” available from UCBRadcure Specialties.

[0117] Other precursor polymer subunits may also be acrylated polyesterpolymers. Acrylated polyesters are the reaction products of acrylic acidwith a dibasic acid/aliphatic diol-based polyester. Examples ofcommercially available acrylated polyesters include those known by thetrade designations “PHOTOMER 5007” (hexafunctional acrylate), and“PHOTOMER 5018” (tetrafunctional tetracrylate) from Henkel Corp.; and“EBECRYL 80” (tetrafunctional modified polyester acrylate), “EBECRYL450” (fatty acid modified polyester hexaacrylate) and “EBECRYL 830”(hexafunctional polyester acrylate) from UCB Radcure Specialties.

[0118] Another preferred precursor polymer subunits is a blend ofethylenically unsaturated oligomer and monomers. For example theprecursor polymer subunits may comprise a blend of an acrylatefunctional urethane oligomer and one or more monofunctional acrylatemonomers. This acrylate monomer may be a pentafunctional acrylate,tetrafunctional acrylate, trifunctional acrylate, difunctional acrylate,monofunctional acrylate polymer, or combinations thereof.

[0119] The precursor polymer subunits may also be an acrylate dispersionlike that described in U.S. Pat. No. 5,378,252 (Follensbee),incorporated herein by reference.

[0120] In addition to thermosetting polymers, thermoplastic binders mayalso be used. Examples of suitable thermoplastic polymers includepolyamides, polyethylene, polypropylene, polyesters, polyurethanes,polyetherimide, polysulfone, polystyrene,acrylonitrile-butadiene-styrene block copolymer,styrene-butadiene-styrene block copolymers, styrene-isoprene-styreneblock copolymers, acetal polymers, polyvinyl chloride and combinationsthereof.

[0121] Water-soluble precursor polymer subunits optionally blended witha thermosetting resin may be used. Examples of water-soluble precursorpolymer subunits include polyvinyl alcohol, hide glue, or water-solublecellulose ethers such as hydroxypropylmethyl cellulose, methyl celluloseor hydroxyethylmethyl cellulose. These binders are reported in U.S. Pat.No. 4,255,164 (Butkze et al.), incorporated herein by reference.

[0122] Initiators

[0123] In the case of precursor polymer subunits containingethylenically unsaturated monomers and oligomers, polymerizationinitiators may be used. Examples include organic peroxides, azocompounds, quinones, nitroso compounds, acyl halides, hydrazones,mercapto compounds, pyrylium compounds, imidazoles, chlorotriazines,benzoin, benzoin alkyl ethers, diketones, phenones, or mixtures thereof.Examples of suitable commercially available, ultraviolet-activatedphotoinitiators have tradenames such as “IRGACURE 651,” “IRGACURE 184,”and “DAROCUR 1173” commercially available from Ciba Specialty Chemicals,Tarrytown, N.Y. Another visible light-activated photoinitiator has thetrade name “IRGACURE 369” commercially available from Ciba GeigyCompany. Examples of suitable visible light-activated initiators arereported in U.S. Pat. Nos. 4,735,632 (Oxman et al.) and 5,674,122 (Krechet al.).

[0124] A suitable initiator system may include a photosensitizer.Representative photosensitizers may have carbonyl groups or tertiaryamino groups or mixtures thereof. Preferred photosensitizers havingcarbonyl groups are benzophenone, acetophenone, benzil, benzaldehyde,o-chlorobenzaldehyde, xanthone, thioxanthone, 9,10-anthraquinone, orother aromatic ketones. Preferred photosensitizers having tertiaryamines are methyldiethanolamine, ethyldiethanolamine, triethanolamine,phenylmethyl-ethanolamine, or dimethylaminoethylbenzoate. Commerciallyavailable photosensitizers include “QUANTICURE ITX,” “QUANTICURE QTX,”“QUANTICURE PTX,” “QUANTICURE EPD” from Biddle Sawyer Corp., New York,N.Y.

[0125] In general, the amount of photosensitizer or photoinitiatorsystem may vary from about 0.01 to 10% by weight, more preferably from0.25 to 4.0% by weight of the components of the precursor polymersubunits.

[0126] Additionally, it is preferred to disperse (preferably uniformly)the initiator in the precursor polymer subunits before addition of anyparticulate material, such as the abrasive particles and/or fillerparticles.

[0127] In general, it is preferred that the precursor polymer subunitsbe exposed to radiation energy, preferably ultraviolet light or visiblelight, to cure or polymerize the precursor polymer subunits. In someinstances, certain abrasive particles and/or certain additives willabsorb ultraviolet and visible light, which may hinder proper cure ofthe precursor polymer subunits. This occurs, for example, with ceriaabrasive particles. The use of phosphate containing photoinitiators, inparticular acylphosphine oxide containing photoinitiators, may minimizethis problem. An example of such an acylphosphate oxide is2,4,6-trimethylbenzoyldiphenylphosphine oxide, which is commerciallyavailable from BASF Corporation, Ludwigshafen, Germany, under the tradedesignation “LUCIRIN TPO-L.” Other examples of commercially availableacylphosphine oxides include “DAROCUR 4263” and “DAROCUR 4265”commercially available from Ciba Specialty Chemicals.

[0128] Cationic initiators may be used to initiate polymerization whenthe binder is based upon an epoxy or vinyl ether. Examples of cationicinitiators include salts of onium cations, such as arylsulfonium salts,as well as organometallic salts such as ion arene systems. Otherexamples are reported in U.S. Pat. Nos. 4,751,138 (Tumey et al.);5,256,170 (Harmer et al.); 4,985,340 (Palazotto); and 4,950,696, allincorporated herein by reference.

[0129] Dual-cure and hybrid-cure photoinitiator systems may also beused. In dual-cure photoiniator systems, curing or polymerization occursin two separate stages, via either the same or different reactionmechanisms. In hybrid-cure photoinitiator systems, two curing mechanismsoccur at the same time upon exposure to ultraviolet/visible orelectron-beam radiation.

[0130] Backing

[0131] A variety of backing materials are suitable for the abrasivearticle of the present invention, including both flexible backings andbackings that are more rigid. Examples of typical flexible abrasivebackings include polymeric film, primed polymeric film, metal foil,cloth, paper, vulcanized fiber, nonwovens and treated versions thereofand combinations thereof. The thickness of a backing generally rangesbetween about 20 to 5000 micrometers and preferably between 50 to 2500micrometers.

[0132] Alternatively, the backing may be fabricated from a porousmaterial such as a foam, including open and closed cell foam.

[0133] Examples of more rigid backings include metal plates, ceramicplates, and the like. Another example of a suitable backing is describedin U.S. Pat. No. 5,417,726 (Stout et al.) incorporated herein byreference. The backing may also consist of two or more backingslaminated together, as well as reinforcing fibers engulfed in apolymeric material as disclosed in U.S. Pat. No. 5,573,619 (Benedict etal.).

[0134] The backing may be a sheet like structure that was previouslyconsidered in the art to be an attachment system. For example thebacking may be a loop fabric, having engaging loops on the oppositesecond major surface and a relatively smooth first major surface. Theshaped structures are adhered to the first major surface. Examples ofloop fabrics include stitched loop, Tricot loops and the like.Additional information on suitable loop fabrics may be found in U.S.Pat. Nos. 4,609,581 (Ott) and 5,254,194 (Ott) both incorporated hereinafter by reference. Alternatively the backing may be a sheet likestructure having engaging hooks protruding from the opposite secondmajor surface and a relatively smooth first major surface. The shapedstructures are adhered to the first major surface. Examples of suchsheet like structures with engaging hooks may be found in U.S. Pat. Nos.5,505,747 (Chesley), 5,667,540 (Chesley), 5,672,186 (Chesley) and6,197,076 (Braunschweig) all incorporated herein after by reference.During use, the engaging loops or hooks are designed to interconnectwith the appropriate hooks or loops of a support structure such as aback up pad.

[0135] Shaped Structures

[0136] The shaped structures may be fabricated out of any suitablematerial, including: nonwovens, foam (open and closed cell foam),polymeric film, polymeric material (both thermosetting and thermoplasticpolymers). Examples of thermosetting polymers include: phenolic, epoxy,acrylate, urethane, urea-formaldehyde, melamine-formaldehyde and thelike. Examples of thermoplastic polymers include: polyurethane, nylon,polypropylene, polyethylene, polyester, acyrnonitrile butadiene stryene,stryene, and the like.

[0137] Heights of backing raised portions may range from about 0.05millimeters to about 20 millimeters, typically about 0.1 to about 10millimeters and preferably about 0.25 to about 5 millimeters. Heights ofabrasive coating raised portions range from about 5 micrometers (μm) toabout 1000 μm, typically about 25 μm to about 500 μm and preferablyabout 25 μm to about 250 μm.

[0138] Ratio of backing height raised portions to abrasive coatingraised portions may be in the range of about 1:1 to 1000:1, typicallyabout 2:1 to 500:1 and preferably about 5:1 to 100:1.

[0139] The shaped structures may be bonded to the backing oralternatively the shaped structures may be unitary with the backing.

[0140] An Abrasive Composite Layer

[0141] An abrasive composite layer of this invention typically comprisesa plurality of abrasive particles fixed and dispersed in precursorpolymer subunits, but may include other additives such as couplingagents, fillers, expanding agents, fibers, antistatic agents,initiators, suspending agents, photosensitizers, lubricants, wettingagents, surfactants, pigments, dyes, UV stabilizers and suspendingagents. The amounts of these additives are selected to provide theproperties desired.

[0142] The abrasive composite may optionally include a plasticizer. Ingeneral, the addition of the plasticizer will increase the credibilityof the abrasive composite and soften the overall binder composition. Insome instances, the plasticizer will act as a diluent for the precursorpolymer subunits. The plasticizer is preferably compatible with theprecursor polymer subunits to minimize phase separation. Examples ofsuitable plasticizers include polyethylene glycol, polyvinyl chloride,dibutyl phthalate, alkyl benzyl phthalate, polyvinyl acetate, polyvinylalcohol, cellulose esters, silicone oils, adipate and sebacate esters,polyols, polyols derivatives, t-butylphenyl diphenyl phosphate,tricresyl phosphate, castor oil, or combinations thereof. Phthalatederivatives are one type of preferred plasticizers.

[0143] The abrasive particle, or abrasive coating, may further comprisesurface modification additives include wetting agents (also sometimesreferred to as surfactants) and coupling agents. A coupling agent canprovide an association bridge between the precursor polymer subunits andthe abrasive particles. Additionally, the coupling agent can provide anassociation bridge between the binder and the filler particles. Examplesof coupling agents include silanes, titanates, and zircoaluminates.

[0144] In addition, water and/or organic solvent may be incorporatedinto the abrasive composite. The amount of water and/or organic solventis selected to achieve the desired coating viscosity of precursorpolymer subunits and abrasive particles. In general, the water and/ororganic solvent should be compatible with the precursor polymersubunits. The water and/or solvent may be removed followingpolymerization of the precursor, or it may remain with the abrasivecomposite. Suitable water soluble and/or water sensitive additivesinclude polyvinyl alcohol, polyvinyl acetate, or cellulosic basedparticles.

[0145] Examples of ethylenically unsaturated diluents or monomers can befound in U.S. Pat. No. 5,236,472 (Kirk et al.), incorporated herein byreference. In some instances these ethylenically unsaturated diluentsare useful because they tend to be compatible with water. Additionalreactive diluents are disclosed in U.S. Pat. No. 5,178,646 (Barber etal.), incorporated herein by reference.

[0146] Abrasive Composite Structure Configuration

[0147] An abrasive article of this invention contains an abrasivecoating with at least one abrasive composite layer that includesplurality of shaped, preferably precisely shaped, abrasive compositestructures. The term “shaped” in combination with the term “abrasivecomposite structure” refers to both “precisely shaped” and “irregularlyshaped” abrasive composite structures. An abrasive article of thisinvention may contain a plurality of such shaped abrasive compositestructures in a predetermined array on a backing. Alternatively, theshaped abrasive composites may be in a random shape or an irregularplacement on the backings. An abrasive composite structure can beformed, for example, by curing the precursor polymer subunits whilebeing borne on the backing and in the cavities of the production tool.

[0148] The shape of the abrasive composites structures may be any of avariety of geometric configurations. Typically the base of the shape incontact with the backing has a larger surface area than the distal endof the composite structure. The shape of the abrasive compositestructure may be selected from among a number of geometric solids suchas a cubic, cylindrical, prismatic, parallelepiped, pyramidal, truncatedpyramidal, conical, hemispherical, truncated conical, or posts havingany cross section. Generally, shaped composites having a pyramidalstructure have three, four, five or six sides, not including the base.The cross-sectional shape of the abrasive composite structure at thebase may differ from the cross-sectional shape at the distal end. Thetransition between these shapes may be smooth and continuous or mayoccur in discrete steps. The abrasive composite structures may also havea mixture of different shapes. The abrasive composite structures may bearranged in rows, spiral, helix, or lattice fashion, or may be randomlyplaced.

[0149] The sides forming the abrasive composite structures may beperpendicular relative to the backing, tilted relative to the backing ortapered with diminishing width toward the distal end. An abrasivecomposite structure with a cross section that is larger at the distalend than at the back may also be used, although fabrication may be moredifficult.

[0150] The height of each abrasive composite structure is preferably thesame, but it is possible to have composite structures of varying heightsin a single fixed abrasive article. The height of the compositestructures generally may be less than about 2000 micrometers, and moreparticularly in the range of about 25 to 1000 micrometers. The diameteror cross sectional width of the abrasive composite structure can rangefrom about 5 to 500 micrometers, and typically between about 10 to 250micrometers.

[0151] The base of the abrasive composite structures may abut oneanother or, alternatively, the bases of adjacent abrasive composites maybe separated from one another by some specified distance.

[0152] The linear spacing of the abrasive composite structures may rangefrom about 1 to 24,000 composites/cm² and preferably at least about 50to 15,000 abrasive composite structures/cm². The linear spacing may bevaried such that the concentration of composite structures is greater inone location than in another. The area spacing of composite structuresranges from about 1 abrasive composite structure per linear cm to about100 abrasive composite structures per linear cm and preferably betweenabout 5 abrasive composite structures per linear cm to about 80 abrasivecomposites per linear cm.

[0153] The percentage bearing area may range from about 5 to about 95%,typically about 10% to about 80%, preferably about 25% to about 75% andmore preferably about 30% to about 70%.

[0154] The shaped abrasive composite structures are preferably set outon a backing, or a previously cured abrasive composite layer, in apredetermined pattern. Generally, the predetermined pattern of theabrasive composite structures will correspond to the pattern of thecavities on the production tool. The pattern is thus reproducible fromarticle to article.

[0155] In one embodiment, an abrasive article of the present inventionmay contain abrasive composite structures in an array. With respect to asingle abrasive composite layer, a regular array refers to aligned rowsand columns of abrasive composite structures. In another embodiment, theabrasive composite structures may be set out in a “random” array orpattern. By this it is meant that the abrasive composite structures arenot aligned in specific rows and columns. For example, the abrasivecomposite structures may be set out in a manner as described U.S. Pat.No. 5,681,217 (Hoopman et al.). It is understood, however, that this“random” array is a predetermined pattern in that the location of thecomposites is predetermined and corresponds to the location of thecavities in the production tool used to make the abrasive article. Theterm “array” refers to both “random” and “regular” arrays.

[0156] Production Tool

[0157]FIG. 5 shows a roller that was used to make production tool 24 asdepicted in FIG. 2. The following specific embodiment of roller 50 wasused to make production tool 24 which was then used to make the abrasivecomposite structure of the present invention. Roller 50 has a shaft 51and an axis of rotation 52. In this case the patterned surface includesa first set 53 of adjacent circumferential grooves around the roller anda second set 54 of equally spaced grooves deployed at an angle of 30°with respect to the axis of rotation 52.

[0158]FIG. 6 shows an enlarged cross sectional view of a segment of thepatterned surface of roller 50 taken at line 6-6 in FIG. 5 perpendicularto the grooves in set 53. FIG. 6 shows the patterned surface has peaksspaced by distance x which is 54.8 μm apart peak to peak and a peakheight, y, from valley to peak of 55 μm, with an angle z which is 53°.FIG. 7 shows an enlarged cross sectional view of a segment of thepatterned surface of roller 50 taken at line 7-7 in FIG. 5 perpendicularto the grooves in set 54. FIG. 7 shows grooves 55 having an angle wwhich is a 99.5° angle between adjacent peak slopes and valleysseparated by a distance t which is 250 μm and a valley depth s which is55 μm.

[0159] Roller 50 may also be used to make a production tool for formingthe shaped structures 12, according to the method described in U.S. Pat.No. 5,435,816 (Spurgeon et al.), which is incorporated herein byreference. FIG. 8 shows a plan view of exemplary square shapedstructures having post and bearing areas defined by the dimensions a andb. Likewise, FIG. 9 depicts a plan view of exemplary circular shapedstructures having post and bearing areas defined by the dimensions c andd.

[0160] A production tool is used to provide an abrasive composite layerwith an array of either precisely or irregularly shaped abrasivecomposite structures. A production tool has a surface containing aplurality of cavities. These cavities are essentially the inverse shapeof the abrasive composite structures and are responsible for generatingthe shape and placement of the abrasive composite structures. Thesecavities may have any geometric shape that is the inverse shape to thegeometric shapes suitable for the abrasive composites. Preferably, theshape of the cavities is selected such that the surface area of theabrasive composite structure decreases away from the backing.

[0161] The production tool can be a belt, a sheet, a continuous sheet orweb, a coating roll such as a rotogravure roll, a sleeve mounted on acoating roll, or die. The production tool can be composed of metal,(e.g., nickel), metal alloys, or plastic. The metal production tool canbe fabricated by any conventional technique such as photolithography,knurling, engraving, hobbing, electroforming, diamond turning, and thelike. Preferred methods of making metal master tools are described inU.S. Pat. No. 5,975,987 (Hoopman et al.).

[0162] A thermoplastic tool can be replicated off a metal master tool.The master tool will have the inverse pattern desired for the productiontool. The master tool is preferably made out of metal,. e.g., anickel-plated metal such as aluminum, copper or bronze. A thermoplasticsheet material optionally can be heated along with the master tool suchthat the thermoplastic material is embossed with the master tool patternby pressing the two together. The thermoplastic material can also beextruded or cast onto the master tool and then pressed. Thethermoplastic material is cooled to a nonflowable state and thenseparated from the master tool to produce a production tool. Theproduction tool may also contain a release coating to permit easierrelease of the abrasive article from the production tool. Examples ofsuch release coatings include silicones and fluorochemicals.

[0163] Suitable thermoplastic production tools are reported in U.S. Pat.No. 5,435,816 (Spurgeon et al.), incorporated herein by reference.Examples of thermoplastic materials useful to form the production toolinclude polyesters, polypropylene, polyethylene, polyamides,polyurethanes, polycarbonates, or combinations thereof. It is preferredthat the thermoplastic production tool contain additives such asanti-oxidants and/or UV stabilizers. These additives may extend theuseful life of the production tool.

[0164] Method for Making An Abrasive Article

[0165] There are a number of methods to make the abrasive article ofthis invention. In one aspect the abrasive coating comprises a pluralityof precisely shaped abrasive composites. In another aspect the abrasivecoating comprises non-precisely shaped abrasive composites, sometimesreferred to as irregularly shaped abrasive composites. A preferredmethod for making an abrasive article with one abrasive composite layerhaving precisely shaped abrasive composite structures is described inU.S. Pat. Nos. 5,152,917 (Pieper et al) and 5,435,816 (Spurgeon et al.),both incorporated herein by reference. Other descriptions of suitablemethods are reported in U.S. Pat. Nos.: 5,454,844 (Hibbard et al.);5,437,754 (Calhoun); and 5,304,223 (Pieper et al.), all incorporatedherein by reference.

[0166] A suitable method for preparing an abrasive composite layerhaving a plurality of shaped abrasive composite structures includespreparing a curable abrasive composite layer comprising abrasiveparticles, precursor polymer subunits and optional additives; providinga production tool having a front surface; introducing the curableabrasive composite layer into the cavities of a production tool having aplurality of cavities; introducing a backing or previously curedabrasive composite layer of an abrasive article to the curable abrasivecomposite layer; and curing the curable abrasive composite layer beforethe article departs from the cavities of the production tool to form acured abrasive composite layer comprising abrasive composite structures.The curable abrasive composite is applied to the production tool so thatthe thickness of the curable abrasive composite layer is less than orequal to its practical thickness limit.

[0167] An abrasive composite layer that is substantially free of aplurality of precisely shaped abrasive composite structures is made byplacing a curable abrasive composite layer on a backing, or previouslycured abrasive composite layers, independently of a production tool, andcuring the abrasive composite layer to form a cured abrasive compositelayer. The curable abrasive composite layer is applied to a surface sothat the thickness of the abrasive composite layer is less than or equalto its practical thickness limit. Additional abrasive composite layersmay be added to an abrasive article by repeating the above steps.

[0168] The curable abrasive composite layer is made by combiningtogether by any suitable mixing technique the precursor polymersubunits, the abrasive particles and the optional additives. Examples ofmixing techniques include low shear and high shear mixing, with highshear mixing being preferred. Ultrasonic energy may also be utilized incombination with the mixing step to lower the curable abrasive compositeviscosity (the viscosity being important in the manufacture of theabrasive article) and/or affect the rheology of the resulting curableabrasive composite layer. Alternatively, the curable abrasive compositelayer may be heated in the range of 30° C. to 70° C., microfluidized orball milled in order to mix the curable abrasive composite.

[0169] Typically, the abrasive particles are gradually added into theprecursor polymer subunits. It is preferred that the curable abrasivecomposite layer be a homogeneous mixture of precursor polymer subunits,abrasive particles and optional additives. If necessary, water and/orsolvent is added to lower the viscosity. The formation of air bubblesmay be minimized by pulling a vacuum either during or after the mixingstep.

[0170] The coating station can be any conventional coating means such asdrop die coater, knife coater, curtain coater, roll coater, vacuum diecoater or a die coater. A preferred coating technique is a vacuum fluidbearing die reported in U.S. Pat. Nos. 3,594,865; 4,959,265 (Wood); and5,077,870 (Melbye), which are incorporated herein by reference. Duringcoating, the formation of air bubbles is preferably minimized.

[0171] In another variation, both the shaped portion of the shaped,flexible backing and the shaped abrasive composite may be molded from asingle tooling using one or two sequential coating operations. Thetooling may contain the mirror image of the combination of the shapedbacking features 12 and shaped abrasive composite features 13 shown inFIG. 1. This production tool may be completely filled with the abrasiveslurry in a single coating step. Alternatively, the production tool maybe filled in two sequential coating steps, the first of which onlypartially fills the tool with the abrasive slurry and the second ofwhich fills the remainder of the tool with a second resin or slurry. Aswith the shape of the shaped features of the backing, and with theabrasive slurry of the first coating, this second resin or slurry may betailored to optimize the performance of the resulting abrasive article.In a two-step coating operation, the first coating operation ispreferably accomplished by means of the aforementioned vacuum fluidbearing die method or slide die coating method reported in U.S. Pat. No.5,741,549 (Maier et al.).

[0172] After the production tool is coated, the backing, or previouslycured abrasive composite layer of an abrasive article, and the nextlayer of curable abrasive composite is brought into contact by any meanssuch that the next layer of curable abrasive composite wets a surface ofthe backing or previously cured abrasive composite layer. The curableabrasive composite layer is brought into contact with the backing or thepreviously cured abrasive composite layer by contacting the nip rollwhich forces the resulting construction together. The nip roll may bemade from any material; however, the nip roll is preferably made from astructural material such as metal, metal alloys, rubber or ceramics. Thehardness of the nip roll may vary from about 30 to 120 durometer,preferably about 60 to 100 durometer, and more preferably about 90durometer.

[0173] Next, energy is transmitted into the curable abrasive compositelayer by an energy source to at least partially cure the precursorpolymer subunits. The selection of the energy source will depend in partupon the chemistry of the precursor polymer subunits, the type ofproduction tool as well as other processing conditions. The energysource should not appreciably degrade the production tool or backing.Partial cure of the precursor polymer subunits means that the precursorpolymer subunits is polymerized to such a state that the curableabrasive composite layer does not flow when inverted in the productiontool. If needed, the precursor polymer subunits may be fully cured afterit is removed from the production tool using conventional energysources.

[0174] After at least partial cure of the precursor polymer subunits,the production tool and abrasive article are separated. If the precursorpolymer subunits are not essentially fully cured, the precursor polymersubunits can then be essentially fully cured by either time and/orexposure to an energy source. Finally, the production tool is rewound ona mandrel so that the production tool can be reused again and the fixedabrasive article is wound on another mandrel.

[0175] In another variation of this first method, the curable abrasivecomposite layer is coated onto the backing and not into the cavities ofthe production tool. The curable abrasive composite layer coated backingis then brought into contact with the production tool such that theslurry flows into the cavities of the production tool. The remainingsteps to make the abrasive article are the same as detailed above.

[0176] It is preferred that the precursor polymer subunits are cured byradiation energy. The radiation energy may be transmitted through thebacking or through the production tool. The backing or production toolshould not appreciably absorb the radiation energy. Additionally, theradiation energy source should not appreciably degrade the backing orproduction tool. For instance, ultraviolet light can be transmittedthrough a polyester backing. Alternatively, if the production tool ismade from certain thermoplastic materials, such as polyethylene,polypropylene, polyester, polycarbonate, poly(ether sulfone),poly(methyl methacrylate), polyurethanes, polyvinylchloride, orcombinations thereof, ultraviolet or visible light may be transmittedthrough the production tool and into the slurry. For thermoplastic basedproduction tools, the operating conditions for making the fixed abrasivearticle should be set such that excessive heat is not generated. Ifexcessive heat is generated, this may distort or melt the thermoplastictooling.

[0177] The energy source may be a source of thermal energy or radiationenergy, such as electron beam, ultraviolet light, or visible light. Theamount of energy required depends on the chemical nature of the reactivegroups in the precursor polymer subunits, as well as upon the thicknessand density of the binder slurry. For thermal energy, an oventemperature of from about 50° C. to about 250° C. effect on shapedstructure and/or backing, and a duration of from about 15 minutes toabout 16 hours are generally sufficient. Electron beam radiation orionizing radiation may be used at an energy level of about 0.1 to about10 Mrad, preferably at an energy level of about 1 to about 10 Mrad.Ultraviolet radiation includes radiation having a wavelength within arange of about 200 to about 400 nanometers, preferably within a range ofabout 250 to 400 nanometers. Visible radiation includes radiation havinga wavelength within a range of about 400 to about 800 nanometers,preferably in a range of about 400 to about 550 nanometers.

[0178] The resulting cured abrasive composite layer will have theinverse pattern of the production tool. By at least partially curing orcuring on the production tool, the abrasive composite layer has aprecise and predetermined pattern.

[0179] There are many methods for making abrasive composites havingirregularly shaped abrasive composites. While being irregularly shaped,these abrasive composites may nonetheless be set out in a predeterminedpattern, in that the location of the composites is predetermined. In onemethod, curable abrasive composite is coated so that the thickness ofthe abrasive composite layer is within the practical thickness limits ofthe composite, into cavities of a production tool to generate theabrasive composites. The production tool may be the same production toolas described above in the case of precisely shaped composites. However,the curable abrasive composite layer is removed from the production toolbefore the precursor polymer subunits is cured sufficiently for it tosubstantially retain its shape upon removal from the production tool.Subsequent to this, the precursor polymer subunits are cured. Since theprecursor polymer subunits are not cured while in the cavities of theproduction tool, this results in the curable abrasive composite layerflowing and distorting the abrasive composite shape.

[0180] In another method of making irregularly shaped composites, thecurable abrasive composite can be coated onto the surface of arotogravure roll. The backing comes into contact with the rotogravureroll and the curable abrasive composite wets the backing. Therotogravure roll then imparts a pattern or texture into the curableabrasive composite. Next, the slurry/backing combination is removed fromthe rotogravure roll and the resulting construction is exposed toconditions to cure the precursor polymer subunits such that an abrasivecomposite is formed. A variation of this process is to coat the curableabrasive composite onto the backing and bring the backing into contactwith the rotogravure roll.

[0181] The rotogravure roll may impart desired patterns such as ahexagonal array, ridges, lattices, spheres, pyramids, truncatedpyramids, cones, cubes, blocks, or rods. The rotogravure roll may alsoimpart a pattern such that there is a land area between adjacentabrasive composites. This land area can comprise a mixture of abrasiveparticles and binder. Alternatively, the rotogravure roll can impart apattern such that the backing is exposed between adjacent abrasivecomposite shapes. Similarly, the rotogravure roll can impart a patternsuch that there is a mixture of abrasive composite shapes.

[0182] Another method is to spray or coat the curable abrasive compositelayer through a screen to generate a pattern and the abrasivecomposites. Then the precursor polymer subunits are cured to form theabrasive composite structures. The screen can impart any desired patternsuch as a hexagonal array, ridges, lattices, spheres, pyramids,truncated pyramids, cones, cubes, blocks, or rods. The screen may alsoimpart a pattern such that there is a land area between adjacentabrasive composite structures. This land area can comprise a mixture ofabrasive particles and binder. Alternatively, the screen may impart apattern such that the backing is exposed between adjacent abrasivecomposite structures. Similarly, the screen may impart a pattern suchthat there is a mixture of abrasive composite shapes. This process isreported in U.S. Pat. No. 3,605,349 (Anthon), incorporated herein byreference.

[0183] Attachment System

[0184] The abrasive article of the invention may be secured to a supportstructure, commonly referred to as a backup pad. The abrasive articlemay be secured by means of a pressure sensitive adhesive, hook and loopattachment or some mechanical means.

[0185] The pressure sensitive adhesive must have sufficient adhesivestrength to secure the coated abrasive to a support pad during use. Forexample, a typical coated abrasive disc/support pad composite may rotateas many as 6,000 revolutions per minute. Representative examples ofpressure sensitive adhesives suitable for this invention include latexcrepe, rosin, acrylic polymers and copolymers e.g., polybutylacrylate,polyacrylate ester, vinyl ethers, e.g., polyvinyl n-butyl ether, vinylacetate adhesives, alkyd adhesives, rubber adhesives, e.g., naturalrubber, synthetic rubber, chlorinated rubber, and mixtures thereof. Onepreferred pressure sensitive adhesive is an isooctylacrylate:acrylicacid copolymer. The pressure sensitive adhesive may be coated out oforganic solvent, water or be coated as a hot melt adhesive.

[0186] The back side of the abrasive article may contain a loopsubstrate. The purpose of the loop substrate is to provide a means thatthe abrasive article can be securely engaged with hooks from a supportpad. The loop substrate may be laminated to the coated abrasive backingby any conventional means. The loop substrate may be laminated prior tothe application of the make coat precursor or alternatively, the loopsubstrate may be laminated after the application of the make coatprecursor. In another aspect, the loop substrate may in essence be thecoated abrasive backing. The loop substrate may be a chenille stitchedloop, a stitchbonded loop substrate or a brushed loop substrate (e.g.,brushed nylon). Examples of typical loop backings are further describedin U.S. Pat. Nos. 4,609,581 and 5,254,194 all incorporated herein afterby reference. The loop substrate may also contain a sealing coat to sealthe loop substrate and prevent subsequent coatings from penetrating intothe loop substrate.

[0187] Likewise, the back side of the abrasive article may contain aplurality of hooks; these hooks are typically in the form of sheet likesubstrate having a plurality of hooks protruding therefrom. These hookswill then provide the engagement between the coated abrasive article anda support pad that contains a loop fabric. This hook substrate may belaminated to the coated abrasive backing by any conventional means.

Test Procedures

[0188] The following test procedures were used to evaluate resincompositions and coated abrasive articles of the present invention.

[0189] Wet SCHIEFER Test

[0190] Abrasive coatings were laminated to a sheet-like backing bearingflattened engaging projections available from 3M Company under the tradedesignation HOOK-IT II™ backing and converted into 4-inch (10.16 cm.)discs. The back-up pad was secured to the driven plate of a SCHIEFERAbrasion Tester, available from Frazier Precision Company, Gaithersburg,Md., which had been plumbed for wet testing. Disc shaped acrylic plasticworkpieces, 10.16 cm (4-inch) outside diameter by 1.27 cm (0.5-inch)thick, available under the trade designation “POLYCAST” acrylic plasticwere obtained from Sielye Plastics, Bloomington, Minn. The water flowrate was set to 60 grams per minute. A 454 grams (one-pound) weight wasplaced on the abrasion tester weight platform and the mounted abrasivespecimen lowered onto the workpiece and the machine turned on. Themachine was set to run for 90 cycles in 30 cycle intervals. Surfacefinish values Rz were measured at four locations on the workpiece foreach 30 cycle interval, with each test sample run in triplicate.

[0191] Panel Test

[0192] 15.2 cm (6-inch) diameter circular specimens were cut from theabrasive test material and attached to a DYNABRADE model 56964 finefinish sander, available from Dynabrade Co., Clarence, N.Y. Abrasiontests were run for a total of one minute, in 10, 20 and 30 secondintervals over three adjacent sections of the test panel, at an airpressure of 344 kPa (50 psi). The test panels were black base coat/clearcoat painted cold rolled steel panels (E-coat: ED5000; Primer: 764-204;Base coat: 542AB921; Clear coat: RK8010A), obtained from ACTLaboratories, Inc., Hillsdale, Mich. Surface finish values Rz weremeasured at five points on each test panel section, with each testsample run in triplicate.

[0193] Surface Finish

[0194] Rz is the average individual roughness depths of a measuringlength, where an individual roughness depth is the vertical distancebetween the highest point and the lowest point.

[0195] The surface finish of abraded workpieces by the Wet SCHIEFER Testand Panel Test were measured using a profilometer under the tradedesignation “PERTHOMETER MODEL M4P,” from Marh Corporation, Cincinnati,Ohio.

EXAMPLES

[0196] The following abbreviations are used in the examples. All parts,percentages and ratios in the examples are by weight unless statedotherwise:

[0197] CN973J75 urethane-acrylate resin from Sartomer, Inc., Exton, Pa.

[0198] F80 expandable polymeric microspheres, trade designation“MICROPEARL F80-SD1,” available from Pierce-Stevens Corp., Buffalo, N.Y.

[0199] SR339 2-phenoxyethyl acrylate from Sartomer, Inc., Exton, Pa.

[0200] SR351 trimethylolpropane triacrylate resin from Sartomer, Inc.,Exton, Pa.

[0201] PD9000 anionic polyester dispersant, trade designation “ZEPHRYMPD 9000,” available from Uniqema, Wilmington, Del.

[0202] A-174 γ-methacryloxypropyltrimethoxy silane, trade designation“SILQUEST A-174,” available Crompton Corp., Friendly, W. Va.

[0203] TPO-L phosphine oxide, trade designation “LUCIRIN TPO-L,”available from BASF Chemicals, Ludwigshafen, Germany.

[0204] GC1000 green silicon carbide mineral, grade JIS1000, availablefrom Fujimi Corp., Elmhurst, Ill.

[0205] GC1500 green silicon carbide mineral, grade JIS1500, availablefrom Fujimi Corp., Elmhurst, Ill.

[0206] GC2000 green silicon carbide mineral, grade JIS2000, availablefrom Fujimi Corp., Elmhurst, Ill.

[0207] GC2500 green silicon carbide mineral, grade JIS2500, availablefrom Fujimi Corp., Elmhurst, Ill.

[0208] GC3000 green silicon carbide mineral, grade JIS3000, availablefrom Fujimi Corp., Elmhurst, Ill.

[0209] GC4000 green silicon carbide mineral, grade JIS4000, availablefrom Fujimi Corp., Elmhurst, Ill.

[0210] In all Examples, both the shaped backing features and shapedabrasive composite features were molded from polypropylene toolings thatcontained the mirror-image 3-dimensional pattern of the desiredfeatures. In all cases, the polypropylene tooling used to form theshaped abrasive composite was made according to U.S. Pat. No. 5,435,816(Spurgeon et al.). Likewise, the shaped backing features in Examples 7through 16, were also formed using tooling made according to U.S. Pat.No. 5,435,816.

[0211] In Examples 1 through 6, the shaped backing features were moldedfrom polypropylene tooling sheets that were made from 48 cm×48 cmstainless steel master toolings. These master toolings were made via amasking/chemical etching process. From these master toolings,reverse-image polypropylene toolings were made using the followingprocess: In a 135° C. heated press, a metal master tooling was placed onthe bottom platen. On top of the tooling was placed a 0.8 mm thick sheetof polypropylene followed by a 3 mm thick aluminum plate. The compositewas pressed at 618 kPa (90 psi) for 3 minutes and then removed. Themirror-image of the master tooling was molded into the polypropylenesheet. This molded polypropylene sheet was subsequently used as thetooling mold to produce the non-abrasive shaped structures on thebacking. This process was repeated for each different tooling used inExamples 1 through 6.

Example 1

[0212] Pre-mix #1: 60.8 parts CN973J75, 36.4 parts SR339 and 2.8 partsTPO-L were combined using a mixer, available under the trade designationDISPERSATOR from Premier Mill Corp., Reading, Pa., at room temperatureuntil air bubbles had dissipated.

[0213] Slurry #1: 3.4 parts of pre-expanded F80 was then added to 96.6parts of Pre-mix #1 and formed into homogeneous slurry #1 using theDISPERSATOR mixer. F80 microspheres were pre-expanded at 160° C. for 60minutes before use.

[0214] Slurry #1 was then applied, via hand spread, to a microreplicatedtooling having square posts, 1.3 mm×1.3 mm×0.356 mm deep, with a 22%bearing area, as described in Table 3. The slurry filled tooling wasthen laminated face down to the smooth side of corona treated backingavailable from 3M Company under the trade designation 3M HOOK-IT II™backing by passing through a set of rubber nip rolls at 26 cm/min. and anip pressure of 275 kPa (40 psi). The slurry was then cured by passingtwice through a UV processor, available from American UltravioletCompany, Murray Hill, N.J., using two V-bulbs in sequence operating at157.5 watts/cm (400 W/inch) and a web speed of 914 cm/min. The toolingwas then removed to reveal a large scale 3-dimensional cured polymerfoam structure having the mirror image of the tooling.

[0215] Pre-Mix #2: 33.6 parts SR339 was mixed by hand with 50.6 partsSR351, into which 8 parts PD 9000 was added and held at 60° C. untildissolved. The solution was cooled to room temperature. To this wasadded 2.8 parts TPO-L and 5 parts A-174 and the mixture again stirreduntil homogeneous.

[0216] Slurry #2: 61.5 parts GC2500 was incorporated into 38.5 parts ofpre-mix #2 using the dispersator mixer to form homogeneous slurry #2.

[0217] The abrasive slurry was then applied, via hand spread, to apolypropylene microreplicated tooling, as depicted in FIGS. 6 and 7wherein: s=55 μm; t=250 μm; w=99.53°; x=54.84 μm, y=55 μm; z=53.00°. Theabrasive slurry filled tooling and was then laminated face down on the3M HOOK-IT II™ backed large scale 3-dimensional coated structure bypassing through a set of rubber nip rolls at 26 cm/min and a nippressure of 275 kPa (40 psi). The slurry was then cured by passing twicethrough the UV Processor using two V-bulbs in sequence operating at157.5 watts/cm (400 W/inch) and a web speed of 914 cm/min. On the firstpass a 6 mm quartz plate was placed over the laminate in order tomaintain pressure on the laminate. The tooling was then separated fromthe backing to reveal a cured 3-dimensional abrasive coating on top of a3-dimensional foam structure.

Example 2

[0218] A 3-dimensional abrasive coating on top of 3-dimensional foamstructure was prepared as outlined in Example 1, wherein slurry #1 wasapplied to a microreplicated tooling having the same square posts butwith a 32% bearing area, as described in Table 3.

Example 3

[0219] A 3-dimensional abrasive coating on top of 3-dimensional foamstructure was prepared as outlined in Example 1, wherein slurry #1 wasapplied to a microreplicated tooling having the same square posts butwith a 42% bearing area, as described in Table 3.

Example 4

[0220] A 3-dimensional abrasive coating on top of 3-dimensional foamstructure was prepared as outlined in Example 1, wherein slurry #1 wasapplied to a microreplicated tooling having the same square posts butwith a 52% bearing area, as described in Table 3.

Example 5

[0221] A 3-dimensional abrasive coating on top of 3-dimensional foamstructure was prepared as outlined in Example 1, wherein slurry #1 wasapplied to a microreplicated tooling having square posts, 10 mm×10mm×0.533 mm deep, with a 90% bearing area, as described in Table 3.

Example 6

[0222] A 3-dimensional abrasive coating on top of 3-dimensional foamstructure was prepared as outlined in Example 1, wherein slurry #1 wasapplied to a microreplicated tooling having round posts, 7 mmdiameter×0.533 mm deep, with a 50% bearing area, as described in Table3.

Example 7

[0223] A 3-dimensional abrasive coating on top of 3-dimensional foamstructure was prepared as outlined in Example 1, wherein slurry #1 wasapplied to a microreplicated tooling having square posts, 2.6 mm×2.6mm×0.533 mm deep, with a 42% bearing area, as described in Table 3.

Example 8

[0224] A double-sided adhesive coated {fraction (1/16)}-inch (1.6 mm)thick polyethylene foam tape, reference number 4496W, available from 3MCompany, St. Paul, Minn., was laminated to the smooth side of the coronatreated 3M HOOK-IT II™ backing. A 3-dimensional abrasive coating on topof 3-dimensional structure was then applied to this substrate asoutlined in Example 7, wherein Slurry #1 was substituted with Premix #1.

Example 9

[0225] A sample was prepared as outlined in Example 8, wherein the 1.6mm ({fraction (1/16)}-inch) thick polyethylene foam tape was replaced by0.8 mm ({fraction (1/32)}-inch) thick material, reference 4492W,available from 3M Company, St. Paul, Minn.

Example 10

[0226] A 3-dimensional abrasive coating on top of 3-dimensional foamstructure was prepared as outlined in Example 7, wherein the coronatreated 3M HOOK-IT II™ backing was replaced by 76 μm (3 mil.) polyesterfilm available under the trade designation “SCOTCHPAK” polyester filmfrom 3M Company, St. Paul, Minn.

[0227] The following Examples 11-16 were made using a knife coaterrather than handspread coating.

Example 11

[0228] A 3-dimensional abrasive coating on top of 3-dimensionalstructure was prepared by knife coating pre-mix #1 to a polypropylenetooling having microreplicated tooling having square posts, 2.6 mm×2.6mm×0.533 mm deep, with a 42% bearing area, as described in Table 3. Thecoated tooling was then applied to a 76 μm (3-mil.) polyester filmbacking so that contact was established between the backing and theslurry. The laminated tooling was given a single pass in the UVprocessor using a D-bulb at 236 W/cm (600 W/inch) exposure, at a webspeed of 9.1 m/min. (30 ft./min.) and a nip pressure of 344 kPa (50psi), after which the tooling was removed. Slurry #2 was knife coatedonto a polypropylene tool having a small-feature as depicted in FIGS. 6and 7 wherein: s=55 μm; t=250 μm; w=99.53°; x=54.84 μm, y=55 μm;z=53.00°. The coated tool was then laminated to the large-featurestructure and exposed under the same conditions in the UV processor andthe tooling then removed.

Example 12

[0229] A 3-dimensional abrasive coating on top of 3-dimensionalstructure was prepared as outlined in Example 11, wherein the ratio ofPre-mix #2: GC 2500 was changed from 38.5:61.5 to 34.5:65.5 Pre-mix#2:GC1000 respectively.

Example 13

[0230] A 3-dimensional abrasive coating on top of 3-dimensionalstructure was prepared as outlined in Example 11, wherein the ratio ofPre-mix #2:GC 2500 was changed from 38.5:61.5 to 36.5:63.5 Pre-mix#2:GC1500 respectively.

Example 14

[0231] A 3-dimensional abrasive coating on top of 3-dimensionalstructure was prepared as outlined in Example 11, wherein the ratio ofPre-mix #2:GC 2500 was changed from 38.5:61.5 to 36.5:63.5 Pre-mix#2:GC2000 respectively.

Example 15

[0232] A 3-dimensional abrasive coating on top of 3-dimensionalstructure was prepared as outlined in Example 11, wherein the mineral GC2500 was replaced by GC3000.

Example 16

[0233] A 3-dimensional abrasive coating on top of 3-dimensionalstructure was prepared as outlined in Example 11, wherein the ratio ofPre-mix #2:GC 2500 was changed from 38.5:61.5 to 40.5:59.5 Pre-mix#2:GC4000, respectively.

Comparative Sample

[0234] A coated abrasive foam disc, grade P3000, available under thetrade designation TRIZACT HOOKIT II™, from 3M Company, St Paul, Minn.

[0235] Abrasion Tests

[0236] Results of Wet Schiefer and Panel tests are listed in Table 1 andTable 2 respectively. TABLE 1 Wet Schiefer Test Rz-Initial Rz @ 30Cycles Rz @ 60 Cycles Rz @ 90 Cycles Example μm (μ-inches) μm (82-inches) μm (μ-inches) μm (μ-inches) Comparative Sample 1.79 (70.3) 0.76(30.0) 0.71 (27.9) 0.70 (27.5)  1 1.67 (65.8) 0.77 (30.1) 0.58 (23.0)0.51 (19.9)  2 1.78 (69.9) 0.88 (34.8) 0.69 (27.0) 0.64 (25.3)  3 1.68(66.3) 0.69 (27.2) (0.58) (22.7) 0.54 (21.3)  5¹ 1.71 (67.4) 0.82 (32.1)0.51 (20.0) 0.53 (21.0)  6 1.75 (69.0) 0.73 (28.8) 0.59 (23.3) 0.49(19.3)  7 1.75 (68.9) 0.74 (29.1) 0.63 (24.9) 0.57 (22.3) 11 1.78 (70.2)0.63 (24.9) (0.52) (20.3) 0.47 (18.5) 12 1.79 (70.4) 1.03 (40.6) 0.97(38.3) 0.92 (36.2) 13 1.73 (68.1) 0.77 (30.2) 0.74 (29.0) 0.71 (28.0) 141.82 (71.8) 0.69 (27.2) 0.67 (26.4) 0.64 (25.2) 15 1.81 (71.2) 0.72(28.2) 0.45 (17.8) 0.38 (14.9) 16 1.77 (69.6) 0.84 (32.9) 0.51 (20.1)0.31 (12.2)

[0237] Examples 4 and 10 were not tested. TABLE 2 Panel Test Rz-InitialRz @ 10 secs. Rz @ 30 secs. Rz @ 60 secs. Example μm (μ-inches) μm(μ-inches) μm (μ-inches) μm (μ-inches) Stiction Comparative 1.49 (58.2)0.74 (29.1) 0.65 (25.5) 0.65 (25.5) No Sample  8 1.52 (59.8) 0.62 (24.2)0.59 (23.1) 0.62 (24.5) No  9 1.51 (59.3) 0.63 (24.9) 0.57 (22.5) 0.58(22.7) No 11 1.45 (57.1) 0.56 (21.9) 0.50 (19.7) 0.56 (21.9) No 12 1.44(56.6) 0.97 (38.3) 0.80 (31.3) 0.74 (29.0) No 13 1.44 (56.5) 0.76 (29.90.62 (24.2) 0.61 (23.9) No 16 1.42 (56.0) 0.74 (29.0) 0.66 (25.8) 0.64(25.2) No

[0238] Table 3, read in conjunction with FIGS. 8 and 9, sets forth thetooling dimensions for Examples 1-16. TABLE 3 Tooling Dimensions BearingArea Reference Example (mm) (%) Figure 1 a = 1.3, b = 1.5, 22 8 height =0.356 2 a = 1.3, b = 1.0, 32 8 height = 0.356 3 a = 1.3, b = 0.7, 42 8height = 0.356 4 a = 1.3, b = 0.5, 52 8 height = 0.356 5 a = 10.0, b =0.5, 90 8 height = 0.533 6 c = 7.0,d = 1.8, 50 9 height = 0.0.533 7through 16 a = 2.6, b = 1.4, 42 8 height = 0.533

[0239] In comparing the Comparative Sample to Examples 1 through 11, itis apparent that, after sanding, all finishes were significantly refinedin a short period of time. However, the Examples of the presentinvention provided a finer finish in an even shorter time. Moreover,these results were essentially independent of bearing area in the rangefrom 22% to 90% bearing area. In analyzing the testing results forExamples 11 through 16, it is apparent that the final surface finishbecomes rougher as the grade of abrasive mineral becomes coarser.However, within this trend, Example 14 of Table 1 (made with JIS2000SiC) provided a finer surface finish at all sanding times than theComparative Sample (graded as P3000, which is finer than JIS2000). TheseExamples also demonstrate that the present invention may readily employa range mineral grades.

[0240] The present invention has now been described with reference toseveral embodiments thereof. The foregoing detailed description andexamples have been given for clarity of understanding only. Nounnecessary limitations are to be understood therefrom. It will beapparent to those skilled in the art that many changes can be made inthe embodiments described without departing from the scope of theinvention. Thus, the scope of the present invention should not belimited to the exact details and structures described herein, but ratherby the structures described by the language of the claims, and theequivalents of those structures.

What is claimed is:
 1. An abrasive article comprising: a. a backinghaving a first major surface and an opposite second major surface; b. aplurality of separated shaped non-abrasive structures, each structurehaving an attachment end attached to said first major surface and adistal end spaced from said first major surface with said shapedstructures comprising distal ends being aligned generally in the sameplane; and c. a shaped abrasive coating comprised of abrasive particlesin a bond system having raised areas and depressed areas coated over atleast said distal ends.
 2. The abrasive article of claim 1 whereinshaped structures viewed from above are square.
 3. The abrasive articleof claim 1 wherein said shaped structures viewed from above are round orhexagonal.
 4. The abrasive article of claim 1 wherein said shapedstructures are aligned in rows in at least one direction.
 5. Theabrasive article of claim 1 wherein said shaped structures are alignedin rows in two directions.
 6. The abrasive article of claim 4 whereinthe aligned rows of shaped structures are separated by a channel definedby the space between rows.
 7. The abrasive article of claim 6 whereinsaid channel is free of any abrasive coating.
 8. The abrasive article ofclaim 1 wherein said shaped structures comprise a polymeric material. 9.The abrasive article of claim 1 wherein said shaped structures areunitary with said backing.
 10. The abrasive article of claim 1 whereinsaid shaped structures comprise a foam.
 11. The abrasive article ofclaim 1 wherein said distal ends have a flat surface.
 12. The abrasivearticle of claim 1 wherein said backing is a polymeric film.
 13. Theabrasive article of claim 1 wherein said abrasive coating comprisesprecisely shaped abrasive composites.
 14. The abrasive article of claim1 wherein said abrasive particles have an average particle size lessthan about 60 μm.
 15. The abrasive article of claim 1 wherein saiddistal ends are spaced from said first major surface by at least about0.05 mm.
 16. The abrasive article of claim 1 wherein said distal endsare spaced from said first major surface by about 0.05 mm to about 20mm.
 17. The abrasive article of claim 1 wherein said backing isflexible.
 18. A method of making an abrasive article, said methodcomprising: a. providing a backing having a first major surface and anopposite second major surface; b. applying a plurality of separated,shaped non-abrasive structures to said first major surface, each of saidstructures having an attachment end attached to said first major surfaceand a distal end spaced from said first major surface with said shapedstructures comprising distal ends aligned generally in the same plane;c. coating at least said distal ends with a coating compositioncomprising abrasive particles in a curable composition which will cureto provide a bond system for the abrasive particles; d. imparting ashaped configuration to the coating composition to provide on curing ashaped abrasive coating having raised areas and depressed areas; and e.curing the curable composition.
 19. The method of claim 18 wherein saidplurality of separated, shaped structures are applied by embossing saidbacking.
 20. The method of claim 18 wherein said plurality of separated,shaped structures are applied by filling cavities in a production toolwith a curable composition, contacting the first major surface of thebacking with the curable composition contained within the cavities inthe production tool at least partially curing the curable compositionand separating the production tool from the shaped structures on thebacking.
 21. The method of claim 18 wherein said backing is flexible.22. The method of claim 18 wherein said backing comprises a polymericfilm.
 23. The method of claim 18 wherein said shaped structures viewedfrom above are round.
 24. The method of claim 18 wherein said shapedstructures viewed from above are square.
 25. The method of claim 18wherein said shaped structures are aligned in rows in at least onedirection.
 26. The method of claim 18 wherein said shaped structures arealigned in rows in two directions.
 27. The method of claim 25 whereinthe aligned rows of shaped structures are separated by a channel definedby the space between rows.
 28. The method of claim 27 wherein saidchannel is free of any abrasive coating.
 29. The method of claim 18wherein said shaped structures comprise a polymeric material
 30. Themethod of claim 18 wherein said shaped structures comprise a foam. 31.The method of claim 18 wherein said shaped structures are provided bymolding a curable material having a mold cavity corresponding to theshape of the backing and the shaped structures and at least partiallycuring the curable composition and removing the backing having theshaped structures from the mold.
 32. The method of claim 18 wherein saidabrasive coating is provided filling cavities of a production toolhaving cavities corresponding to the shaped configuration with a mixturecomprising a curable binder composition containing abrasive particles,applying the mixture contained in the cavities to at least the distalends, at least partially curing the binder composition while theproduction tool is in contact with the mixture and removing theproduction tool after said curing.
 33. The method of claim 18 whereinsaid abrasive coating is provided by filling cavities of a productiontool having cavities corresponding to the shaped configuration with amixture comprising a curable binder composition containing abrasiveparticles, applying the mixture contained in the cavities to at leastthe distal ends, removing the production tool and at least partiallycuring the curable composition.
 34. The method of claim 18 wherein thecoating and imparting are accomplished by use of a rotogravure roll. 35.The method of claim 18 wherein said abrasive particles have an averageparticle size less than about 60 μm.
 36. The method of claim 18 whereinsaid distal ends are spaced from said first major surface by at leastabout 0.05 mm.
 37. The method of claim 18 wherein said distal ends arespaced from said first major surface by about 0.05 mm to about 20 mm.38. A method of finishing a surface of a substrate, the methodcomprising: a. contacting a surface of a workpiece with an abrasivearticle comprising: (1) a backing having a first major surface and anopposite second major surface; (2) a plurality of separated shapednon-abrasive structures, each structure having an attachment endattached to said first major surface and a distal end spaced from saidfirst major surface with said shaped structures comprising distal endsbeing aligned generally in the same plane; (3) a shaped abrasive coatingcomprised of abrasive particles in a bond system having raised areas anddepressed areas coated over at least said distal ends; and b. relativelymoving the abrasive article and/or the workpiece to modify the surfaceof the workpiece.
 39. The method of claim 38 wherein said workpiecesurface is painted.
 40. The method of claim 38 further comprisingintroducing a fluid to the contacting surface of the workpiece and theabrasive article.
 41. The method of claim 38 wherein said fluid iswater.
 42. The method of claim 38 wherein said abrasive article movingis a random orbital moving.